Machine tool control



6 Sheets-Sheet 1 Filed Nov. 6, 1946 l I I I l I l IIJJIIIIIIIII Il l n IIIIIIIIILP l I l l l l INVENTOR. CLARENCE JOHNSON April 15, 1952 c. .JOHNSON MACHINE Toor. CONTROL 6 Sheets-Sheet 2 FIG;

INVENTOR.

CLARENCE JOHNSON ATT EY Filed NOV. 6, 1946 April 15 1952 c. JoHNsoN 2,593,310

- MACHINE TOOL CONTROL Filed Nov. 6, 1946 6 Sheds-Sheet 5 El lo' FIG 3 INVENTOR.

A CLARENCE JGHNSON Apfil 15, 1952 c. JOHNSON I 2,593,310

MACHINE TooL CONTROL Filed Nov. 6, 1946 '6 Sheets-Sheet 4I I @I E 1' I w I I E LL I m I R I N \I I I I I I l I r I I m QT INVENTOR.

CLARENCE JOHNSON BY April 15, 1952 c. JOHNSON MACHINE TOOL CONTROL 6 Sheets-Sheet 5 Filed Nov. 6, 1946 ll-M INVENTOR. CLARENCE JOHNSON @WW ATT NEY April 15, 1952 c. .loHlNsoN MACHINE T001. coNTRoL 6 Sheets-Sheet 6 Filed NOV. 6, 1946 FIG. 7

FIG. 8

INVENTOR.

CLARENCE JOHNSON Patented Apr. 15, 195.?.

2,593,31 MACHINE TOOL CONTROL Clarence Johnson, Orfordville, Wist, assigner to Bailey `Meter Company, a` corporation of Deia- Ware Application November 6, 1946, Serial No. 708,033 2 claims. (ci. sla-14) 1 This invention relates to the art of contour con trol or object duplication and is particularly directed to the provision of apparatus, systemsV and methods for material forming machines whereby a work piece is formed to a contour or configuration determined by a master.. pattern.

template, or the like which dictates the desired conguration.

Specifically, although not limited thereto, the disclosure is directed tothe control and opere ation of a metal working lathe wherein a tracer,`

or tracers, scans a pattern for reproducing` in the Work piece the conguration of the pattern.

In simplest language, the` tracer which scans the pattern provides a valve or port bleeding a pressure iluid such as compressed air to the atmosphere from a substantially constantpressure source. The rate of bleed to theatmosphere` is determined by the freedomof theportunder the` dictates of the tracer and' pattern. The rate of ilow of the air to the atmosphere and the conse quent variations in pressure of the airdue to such variations in rate of discharge are utilized through improved relay mechanisms to control4 iluid motors for power operation of' the'machine. Preferably the fluid motors are actuated by'a hydraulic luid such as oil, andthe motrsmay be piston-cylinder combinationsor rotary iiuidy motors. The general purpose' accomplished: by the powerV devices is .to relatively movethe tracer and tool in regard with the pattern and` workpiece. Such a system combines `.and utilizes the advantages of an air tracer with hydraulic oil power means.

It is quite possible to utilize asingle fluid control and power system wherein the fluid is oil under pressure. Known systems of` this type, however, require a tracer which is of considerable size and complexity. Theiluid leaving the port or other similar opening of thetracer mech#- anism does in my invention discharge freely to the atmosphere adjacent the tracer.

The preferred form of my invention employs a tracer discharging air under a pressure of the` `order'of 35 p. s. i. freely to the atmosphere at a controllable rate. The back pressure resultant is `utilized in a simple relay mechanism ,tocontrol' of a relatively higher pressure incompressible My preferred tracer is of relatively small size and simplicity as com.-

iiuid for the power devices.

Thus I combine the many advantageous 2 pared to known liquid tracers previously men tioned.

In the present invention I utilize what is corn monly termed a rotating master of substantially the same size and conguration as the. desired resultant work piece. Such master is continually scanned'by a plurality of tracers, each of which individually controls a power mechanism for rela-V tively l moving the tool and work piece, while one of the tracers relatively moves itself toward or away from the work piece and the other tracer relatively moves itself along the work piece.

While I illustrate and describe a preferred embodiment of my present invention,l it is of course to be understood that this is by way of example only and not to be considered as limiting. In other words, the fact that I illustrate and describe two tracers controlling piston-cylinder power devices does not limit my present invention below a plurality of tracers controlling fluid pressure power devices.

Obviously a contour control or object duplicator of the type forming the subject matter of my presentinvention may be employed with material formingV machines or machine vtools of variousftypes, such as. milling machines, lathes, slot- A ters, planers, die sinking machines or other machines in which the relative feed between the tool. andthe work may be suitably controlled. I` havejchosen to illustrate and describe my invention as applied particularly to metal turning engine lathes. Further applications and' modifications of my invention will be readily apparent.

In the present embodiment I have found it desirable to utilize a pattern of substantially the exact shape I desire to form the work piece. This greatly simplies the construction of the pattern and the checking oi finished work'. An advantage of my invention is that I may construct' the pattern as required to produceA the desired shape of the work piece.

One object of my invention is to provide an improved contour control for a metal working lathe wherein the master is substantially' a duplicate of the desired work piece, and wherein it is rotated with the vwerk piece.

A- further object is to provide a plurality of tracer mechanisms continuously scanning the master when-the machine is in operation, and so arranged lthat one of the tracers controls the transverse positioning of the tool, the second tracer controls the longitudinal movement of `the tool alongtne axis oi the work piece.

In the drawings:

Fig. 1 is a somewhat diagrammatic plan view of the engine lathe showing particularly the pattern, work piece, tracers and power positioning devices.

Fig. 2 is an enlarged diagrammatic drawing of a portion of Fig. 1.

Figs. 3 and d show two different arrangements of pneumatic and hydraulic circuits in connection with Figs. 1 and 2.

Figs. 5, 6, 7 and 8 are enlarged diagrammatic showings of a portion of the pattern and work piece under different stages of machining.

Referring now to Fig. l, I show my invention applied to an engine lathe I having a head stock 2 adapted to be rotated by any suitable means. A carriage 4 is movable longitudinally along the bed of the lathe on suitable ways 5 and supports a tail stock 3. the bed of the lathe on suitable ways 6 is a carriage 'lvupon which is mounted a cross-slide 8 movable onways 8A transversely of the bed of the lathe. Y

Mounted on and carried by the cross-slide 8 is an angularly positionable compound rest 9 forming a tool support fora tool I5. Movements of the tool I!) relative to a work piece il are produced through the agency or" an hydraulic power device i2 acting longitudinally and through the agency of an hydraulically actuated power device I3 adapted to position the'cross-slide 8 and compound rest 9 transversely along the ways 8A. The hydraulic device It is supported by the carriage l in a manner such that its'piston rod Ill will position the cross-slide 8, compound 9, and tool I5 transversely of the lathe along the ways SA while the entire unit i3 ispositioned with the carriage I axially of the lathe by the power device I2.

Itis evident from the above that the Work piece I I is supported in customary manner between the headstock 2 and the tailstock 3` and is rotated at preselected speeds by the usual meansV (not shown); The cutting tool I is moved longitudinally along the work piece throughthe agency of the-hydraulic means I2 and transversely relative to the work piece through the agency of the hy-A draulic means I3.

or pattern I5 for vdetermining the nal shape of the work piece li.' The pattern I5 is substantially a sample of the desired work piece, although in certain respects it may be distorted so that the finished work piece will'be properly produced. Herein it differs from the finished work piece I I only as to the height of the iin I9 above the main body and for a purpose which will be -la-ter explained. It is supported for rotation between centers I6, Il and is rotated by and with the headstock 2 through the agency of a belt I8 or similar transmission means. It is preferable, in the present embodiment, to have vthe pattern. I5 rotated in the same direction and at the same speed as the work piece I I.

Supported by andl moved with the cross-slide 8 is an extension 25 supporting two tracer assemblies 2I and 22 whose feelers scan the master I5 as the carriage 'l is traveled longitudinally along the Ways 6. I have shown in Fig. 1 that the feeler of the tracer `2| is in engagement with the main body of thepattern I5, while the feeler arm of the tracer 22 is in engagement with the side of the ln I9. With reference to other figures of the drawing the operation will be explained more in detail. Let it suffice here to say that the transverse motor I3 is under the control of the tracer Also movable longitudinally along 2 I, whereas the longitudinal motor I2 is under the control of the tracer 22. l

The particular shape of the pattern I5, which has been chosen for discussion in the present specication, is perhaps somewhat unusual, but it has been chosen purposely from the standpoint of illustrating the versatility of the control system herein described. The particular pattern I5 represents a Venturi shaped nozzle for fluid flow. Its main body has an exterior of a double conical nature, tapered from either end along a curved path to a mid point of lesser diameter than the two ends. This might well be a straight taper or it might be that the general taper from one end to the mid point is of a different inclination or curvature than from the other end to the mid Y point. Y

purposes.

Wrapped around the body of the pattern is a nn or wormlike projection I2 for radiation cooling As shown, the nn I9 is of uniform height or extension outwardly from the main body of the pattern and of a generally uniform thickness. It is, however, shown as being of nonuniform pitch in that the convolutions are closer together at the greater diameter of the pattern than they are at the lesser diameter. particular nozzle being machined these convolutions are so spaced or pitched as to theoretically given a uniform heat transfer to the surrounding atmosphere through the varying spacing of the convolutions in accordance with the varying diameter of the main body pf the nozzle.

After the exterior of the work piece is machined in conformity to the dictates of the'master I5 it will be properly bored to form a Venturi nozzle through which a uid is to be passed. 'Ihe present description will include only the machining of the exterior of the work piece I I in conformity with the dictates of the master I5.

It will be evident that the pattern I5 is representative of a class of object shapes wherein a body portion of relatively lesser diameter has a .more or les-s regular or continuous protuberance like a worm or spiral wrapped around it. An example is the hour-glass worm of an automobile steering mechanism wherein the pitch may be substantially uniform. Another example is the vtapered meat or food grinder worm in which th v pitch is not uniform.

Referring now to Fig. 2, I show therein in very v schematic fashion a portion only of the assembly of Fig. 1. I have rearranged and distorted certain of the parts merely for clarity of understanding in explanation.

It will be observed that the carriage 'I is positioned longitudinally of the lathe along the ways 6 through the agency of the hydraulic motor I2 I5 for scanning the same as the carriage 'I is` moved along the ways 6 from left to right. Also carried by the cross-slide 8 is the tracer assembly y 22 having a tracer arm 25 riding the left-hand surface 26 of the projecting iin I9. Preferably the cooperation of the tracer arm 23 with the body surface 24 of the pattern I5 controls the transverse positioning motor I3, whereas the cooperation of the tracer arm 25with the surface `2li of the nn I9 controls movement of the motor I2.

In the- 3, I will now describe the actual control of the motors I2, I3 by the tracers 22, 2I respectively.'

Air under pressure is supplied from any` convenient source to a shutoiI valve 3I. After passing through a pressure reducing valve 32 the air in the pipe 33 is at a normally constant pressure of about 45 p. s. i., at the entrance to restrictive orifices 34, 35. The outlet of the oriiice 34 is joined by a pipe 36 which communicates with the tracer assembly 2I and with a bellows 31 of a relay generally indicated at 38. The relay 38 is diagrammatically shown as having a pressure receiving bellows or expansible chamber 31, whose movement is opposedl by a loading spring 39 and for positioning a pilot stem 40.

Oil under a relatively high pressure, as for example 200 p. s. i., is utilized as a hydraulic iiuld supplied by a pump 4I, driven by a motor 42, and drawing its supply of oil from a sump 43.

Oil is supplied to the relay 38 through a pipe 44 and drains from the pilot to the sump through o; pipe 45. The hydraulic cylinder I3 is joined at its opposite ends with the pilot valve 3B by way of pipes 46, 41.

As shown in Fig. 3, the pilot stem 45 is in a shutoff or locking position relative to pipes 46, 41, so that movement of the piston rod 48 of the motor I3 is locked against movement. This is the condition which would prevail when the elements 23, 21 of the pilot assembly 2l are in what I have previously termed a normal condifrom the "normaP value as caused by a variation .from the normal relation between the elements 23, 21, then the pilot stem 4I] is positioned either upwardly or downwardly an amount determined by the actual pressure within the pipe 36, eective upon the bellows 31. Such positioning of the pilotstem 46 will result (for example) in oil under high pressure being sup- `l plied through the pipe 41 to the cylinder I3 and being drained from the opposite side of the piston through the pipe 46. This results in a movement of the piston rod 48 in proper direction to follow up the movement of the tracer arm 23 by a follow-up movement of the housing 21, tending to return the interrelation of the elements 23, 21 vto a normal position wherein the pipes 46, 41 are sealed off and further movement of the piston rod 48 is locked.

In other words, for a "normal condition, as represented by cylindrical turning, the pilot stem 40 locks the pipes 46, 41 and thereby locks movement of the piston rod 45. If the pattern surface 24 recedes from the tracer feeler 23, or advances towards it, then the result is a movement of the cross-slide 8 in proper direction to turn the work piece to conformity with the dictates of the masten. and at the same time to cause the tracer housing 21 to follow up (in the saine direction) the prior movement of the feeler 23 in an attempt to regain normal condition.

Referring again to Fig. 3, it will be observed that air through the orifice 35 supplies a pipe49 joining the tracer assembly 22 and the bellows 50 of a variable uid resistance I adapted to control the hydraulic motor I2. The iiuid resistance 5I has a loading spring 52 cooperating with the bellows 50 in the positioning of a` pilot 8. stem 53, the latter constitutinga variable resistance to thev iiow of oil from a pipe 54 to a pipe 55, the latter joining the sump 43.

Inasmuch as it is contemplated that movement of the carriage 1 will be in a single direction dure' ling a, normal lmachining operation (in thisexample from left to right) oil under high pressure .is supplied to thevleft-hand end (Fig. 3) of the cylinder I2 and Vis-relieved from the rightha'nd end thereof. The cil supply to the lefthand end of the cylinder I2 is supplied" under fullpressure from the pump 4| through a pipe 56, a-two-position valve 51, a direction switching valve 58, and-a pipe 59.` The right-hand end of the cylinder I2 is connected by way of a'pipe 60, direction switchingvalve 58, a, pipe 6I, the two-'position valve 51,- a two-pcsitionfvalve 62, and-`the pipe 54,-' through the relay 5I and the pipe 55 to the sump 43; It will thus be observed that speed of travel of the piston 63, and consequently longitudinal travel of the carriage 1, will vdepend entirely upon the rate of release of oil from the right-hand end of vthe cylinder I2, and thus upon the variable restriction interposed by the pilot stem 53 between the pipes 54 and 55.

I have mentioned that longitudinal travel of the carriage 1, in this instance from left to right, is under the control of the tracer 22, and thereby of the inter-relation between elements 25, 28. Inasmuch as the element 25 ridesthe surface 26 of thefspirally wrapped iin I9, it will be seen that the inter-relation between the elements 25, 28 depends upon the pitch of the n I9 around the main body of the pattern I5. Thus the pitch of the iin I9 dictates-the pressure of air within the pipe 49, eiective within the bellows 50, for positioning the restrictor 53 and thus controlling the speed of travel of the piston 63. words, the longitudinal travel of the tool IIIv axially along the work piece II is directly controlled by the positional spacing of the 1in I9 axially along the pattern I5. Thus the speed of travel of the tool I0 axially of the work piece will be at a diierent rate near the ends of the pattern I5 than along the center of the pattern, forv as I have previously pointed out the iin I9 is closer spaced at the ends than in the middle; This, of course, is not a requisite in the operation of "my controlv system, but is an example which I have chosen" as being a somewhat more diY templates a cutting travel of the tool I0 from left to right across the lwork piece II. When such a travel has been completed it is desiredv to retract the cutting tool from engagement with the work piece and rapidly traverse the carriage 1 from right to left to be in position for a second cutting travel. I accomplish this by moving the two-position valves 51, 62 to the position shown in dotted line of the handles thereof. It willbe understood that these two valves are in a common assembly or otherwise so arranged that a single handle may be moved to accomplish'the simultaneous switching of both valves to the dotted line position. In such position it will be observed that oil under pressure, available through the pipe 56, passes through the valve 51 directly `to the pipe 6I, the switching valve 58 and tothe pipe 60. oil is bled vfrom the left-hand end of the cylinder I2 through the pipe 59, switching Valve 58, the valve 51, the valve v62, and the pipe 6,4 to the drain pipe 55 thus byrpassing the variablerestriction In 'other' At the same time.

.mum uniform speed from right to left. erably the limit of travel at either the right or `left end'lis-accomplished by'travel limits arranged ycylinder I 2.

.63, while theleft-hand'side of thepiston is freely 4open to the sump 4ll'aiso that the :piston 63, and

consequently the .carriage 1, is traveled vatmaxi- Prefin cooperation between the cylinder I2 and the piston E3, or its related piston rod. Thus in vthe normal machining cut the tool may be allowed to run off the `right-hand end of vthe work with the piston 63 .stopping the travel'of the tool when `the piston reaches its extreme of ztravel.. After the operator has switched the valves l', 62 the rapid return of ithe tool to the left-hand Vend is freely accomplished .until limited by the extent of motion of the .piston 63 in that direction,

Under certain conditions it will be advisable .to have the normal cutting travel of the ,tool .III operate from right to left. In `this event, Ythe rapid return of the tool Lto a starting position would be from left .to right. .Such a reversal may be accomplished vby moving the handle 65 of the valve 58 to the alternate position `shown dotted in Fig. 3. Under `this condition `the internal lands of the valve 58 iproperly switch the normal incoming oil under high pressure from .admission to the pipe 5e Ato 4admission to the pipe 69. All other functional operation remains the same except that normal cutting travel of Vthe tool III is in this example from "right to left.

Referring now to Fig. 4 I show therein a modication of the air and oil circuits I have 'just described inconnection with Fig. ,3. The arrangement of Fig. 4 has certain advantages under :some conditions `of operation.

Specically, the relay 5I A differs from the relay 5I in that the movable pilot stem 53A has a land 65 variably throttling the oil supply through thepipe 56 to the pipe 56A and the left-hand end of the cylinder I2. The pilot stem 53A alsohas a land B6 variably throttling the drainage pipe 54 position-of the three valves 51, 62A and 6l the oil under pressure through the pipe 55 Vby-"passes the relay 5IA and is admitted `through a pipe 68 to the pipe 55A, the valve 5I, the pipe 6I, the valve 58, pipe 6B, and to the right-hand end of At the same time drainage from the left-hand end of the cylinder I2 is allowed through pipe 59, valve 55, valve 57, valve 62A, and pipe 54A to the sump.

Attention should now be directed to Figs. 5, 6, 7, and 8, which are somewhat diagrammatic representations useful in explaining the actual operation of the system. It Will be observed that in Figs. 5, 6 and 7 I show 'a portion each of the pattern and of the work piece, whereas in Fig. 8

`I .show `a portion only of the `work piece. Referring now in particular to Fig. 5, it will be observed that I show in the upper portion of this figure a horizontal section through the front portion ofthe pattern, in general from the left-hand end to and including the center portion. The

.desired A.surface V24 fis .a curved Iconical decrease vinf diameter from leftto right with a nearlycylindrical vcentral Vportion before `the diameter progressively increases toward the unshown right end-of the master. The nn I9 is of uniform height and thickness, but the height or projection from the surface 24 is greater than that desired on the work piece by an extent indicated at Y. Thisis purposely so that the tracer feeler 23 may be adjusted toward the right until it is in line (radially from the axis of the master) with the contacting end of the tracer feeler 25 without :thetwo entangling orattempting to occupy the Thus by having the effective the :n I9 'represented by X, I simulate the de- .sired portion of the iin I9except that it is spaced away fromtthelsurface `24 bythe amount Y.

InJFig, 5 the work piece I.I is shown as `having its .rough casting outer surface represented at `69. The -desired finished'surface is represented at T0 by dotted line. d

Assuming the rough blankwork piece 69 being rotated and the carriage 'I at some starting position to the left, then the cross-slide 8 is moved toward the 4center line of the workpiece until `the tool I0 engages in cutting fashion as shown by the solid profile IUAV, Fig. 5. Under this condition the feelers 23 and 25 are adjusted to engage the ,pattern I5 as shown at the upper left of Fig. 5.

vIhe work vand pattern are then placed in rotation and a Vsingle spiraling cut is taken across the work from left to right, with the resultant cut shown dotted, as at IBB and IUC. It will be observed that the cut at IDB and IOC is the same distance Z from the left-hand side of the nn sections ISB and ISC as it was from nn section IBA, because the spacing M of the feelers 23, 25 has not Avaried as the carriage 'I moves along 'the ways 6 toward the right. In othei` words, the travel .of the tool longitudinally of the work has followed `the spacing of the fin I9 as the master I5 is rotated, due to contact therewith of the feeler 25. The feeler -23 was followed by the fixed spacing M and thus the cut IDA, IIlB 'and IDC has remained a xed distance Z from the left-hand side of the variably `spaced n I9. At the same time while the tool IIJ started inthe position IGA. cleaning up on the right hand side of the n, it progressively leaves a Wider'uncleaned up area Yuntil the center of the master is passed and 'the n portions progressively approach eachother. Fig. 5 represents the path of the tool, IU in a single traverse longitudinally of the work and `pattern by the carriage 1.

Fig. 6 `illustrates a second cut across the work wherein the tool I0 has been started in an overlapping cut IUD, I GE and IGF. This is accom- `plished by starting the tool at the location IOD and, through 'the adjustment 29, Vshifting the feeler 23 toward the feeler 25, thus reducing the dimension M.

`.Eteferring now 'to Fig. '1 it will be observed that a succession of cuts have been made of substantially 'the same depth until the space hetween the fin portions I SD, IQA. is machined out .and the same width or cut is accomplished spirally throughout the entire length of the workpiece.

The assembly is again moved` to the left to a starting positionand the tool is advanced toward the center `of vthe workpiece for a second succession of cuts to a greater depth between the This is accomplished by proper relative adjustment or" the compound 9 and tracer assembly 2|, 22. While I have generally indifcated the shape of the cutting tool lil as being lsomewhat rounded, it will be appreciated that 'this shape depends upon numerous factors and lthe proper shape will be chosen for the mate- .rial operated upon.

Successive series of spiraling cuts are taken facross the workpiece, each series oi increasing cdepth, and the final series perhaps with a diferently shaped tool, so that a finished contour 'as represented in Fig. 8 in solid line as at 10 results with the desired sharp corners or llets. The result is a spiralling channel cut' into the surface of the workpiece ll of a uniform width Z', which is the desired finished spacing between the rst two sections 19D and I 9A of the fin 19. The next operation may desirably be to contour machine the outer edge 'Il of the iin ISA down to the dotted line desired shape.

It will be observed that the n section ISA, 360 around the workpiece from the starting section ISD, is considerably wider than desired and progressively wider until the center of the workpiece is reached, and then progressively narrower until the right-hand (unshown) end of the workpiece again finds the distance Z as desired. Y

It is next preferable to begin a seriesof machining operations from the right-hand end of the pattern and workpiece with travel of the carriage I from right to` left and to have the feeler 2li tra-ce the right-hand edge of the n I9. Such' a reversal ofnormal travel is accomplished as previously mentioned by switching the hand valvet, whereaiter normal travel of the piston 63 is from right to left. Performing a similar series of cuts to that just described, ex-

cept for the direction of normal travel, the portions 12, 13 will be cleaned ori at both ends of the workpiece, leaving perhaps an unfinished portion 'I4 in the very center of the workpiece. This portion may later be cleaned ofi by properly'moving the elements l0, 2|, and 22.

I have purposely illustrated and described the contourrlnaching of a rather complicated and diicult structure including numerousproblems to clearly illustrate the range of adjustment and operation of my preferred system. The machining operation would be considerably simpliiied if the rin I9 were wrapped around the base of the pattern at a uniform pitch. The operation might be simplified if the double curvature of the base portion were not curved, but were a straight taper. It would be simplied were the base portion cylindrical rather than tapered in any respect. `However, the apparatus and system which I have invented is clearly shown to be applicable to a wide range of complicated turning Yoperations wherein in general it may be said Vthat two tracer assemblies are provided, one of the assemblies primarily controlling the longitudinal travel of the tool along the workpiece while the other assemblyat the same time controls the transverse movement of the tool relative to the workpiece.

While I have illustrated and described a certain preferred embodiment of my invention it will be understood that I am not to be limited thereto inasmuch as the drawing and description are by way of exampleonly.

What I claim as new, and desire to secure by Letters Patent of the Uni-ted` States, is:

1. In combination with a pattern controlled lathe having means for relatively moving a 'tool and workpiece along a nrst path parallel -tothe longitudinal axis of the lathe and along a-fsecond path at an angle to said rst path, .means for mounting a pattern for rotation about an axis parallel to the longitudinal axis of the lathe, means for mounting the workpiece for rotation about an axis in spaced parallel relation to the rotational axis of the pattern, and means for rotating the pattern and the workpiece in syne chronism: a pattern having a body portion with the shape of a surface of revolution and a generally wormlike outward projection from saidV body portion, iirst tracer means continuously scanning the body portion of the pattern for controlling relative movement of the tool and workpiece along said second angular path, and second tracer means continuously and concurrently scanning the lateral surface of the wormlike projection of the pattern that is adjacent the bodyportion being scanned by said rst tracer means for controlling relative movement of the tool and workpiece along said first parallel path.

2. In combination with a pattern controlled lathe having means for relatively moving a tool and workpiece along a first path parallel to 'the longitudinal axis of the lathe and along a second path at an angle to said rst path, means for mounting a pattern for rotation about an axis parallel to the longitudinal axis of the lathe, means for mounting the workpiece for rotation about an axis in spaced parallel relationto the rotational axis of the pattern, and means for rotating the pattern and workpiece in synchronism: a pattern having a body portion. with the shape of a surface of revolution and a livelical iin projection from said body portieri,` said n being of greater height than the iin to be formed on the said workpiece, rst tracer means continuously scanning the body portion of the pattern for controlling relative movement of the tool and workpiece along said second angular path, and second tracer means continuously and concurrently scanning the lateral surface of the fin projection of the pattern that is adjacent the body portion being scanned by said first tracer means for controlling relative movement of the tool and workpiece along said rst parallel path.

. CLARENCE JOHNSON.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED s'rA'rEs PATENTS Switzerland June 30, 1940 

